Vehicles, such as automobiles and trucks for example, include an axle assembly that transmits rotational energy developed by the vehicle engine to the wheels. The axle assembly will typically include a housing having both a hypoid ring and pinion gear set, and a differential gear set. The differential gear set includes a gear train that allows the wheels of the vehicle to turn at different rotational speeds. This allows an outer wheel to rotate faster than the inner wheel during a turn. The housing typically includes a sump that contains a lubricant. The lubricant is moved by one of the hypoid gears, such as the ring gear for example, that causes the lubricant to be distributed within the housing to lubricate the components.
During operation, the rotation of the ring gear causes the lubricant to flow within the housing. As a result of operation as well as changes in temperature, the pressure within the differential housing can increase or decrease (pull vacuum) during operation. Typically, a vent is affixed to or formed in the differential assembly housing. The vent provides a means of equalizing the pressure within the housing with the ambient environment. However, since the lubricant is flowing within the housing, there is a risk that some of the lubricant may be expelled from the differential housing resulting in a decrease in the lubricant level.
Accordingly, it is desirable to provide an axle assembly having a vent that equalizes the housing pressure while reducing the risk of lubricant loss.